Regulation of Posture and Locomotion in Decerebrate and Spinal Animals

Abstract

The experiments reported here showed that decerebrate cats can actively maintain posture during standing and walking. On standing, postural corrections consisted of redistribution of extensor muscle activity in response to perturbations. Correcting reactions during walking included changes in the durations of the swing and transfer phases of the locomotor cycle, modulation of supporting force reactions, and modification of flexor and extensor function. Detailed analysis of correlations between muscle activity, supporting force reactions, and the kinematics of truncal and hindlimb movements showed that the motor system of the decerebrate animal can use a combination of feedback and feedforward to regulate dynamic balance during locomotion. Furthermore, balance was rapidly restored after impairment due to stumbling or perturbing influences. The intraspinal neural networks and somatosensory afferent input from the limbs can effectively regulate balance during walking and standing, without involvement of the vestibular and visual systems. After interruption of the connection with the motor centers of the stem and forebrain in decerebrate and spinal animals, these networks were in a suppressed state but could be activated by epidural and sensory stimulation substituting for tonic supraspinal drive.